The present invention relates generally to athletic boots and more particularly to a closure mechanism for athletic boots such as ski boots.
With the advent of substantially rigid molded plastic shells for ski boots and the like, the means for comfortably but securely closing the shell about the wearer's foot has been of considerable importance. Heretofore, ski boots in particular have been provided in two general designs fitting the forefoot in different ways. According to one design, commonly referred to as front-entry boots, overlapping flaps are provided which, being flexible to some extent, fold over the forefoot to encase it. In the second design, a relatively unyielding shell of fixed shape surrounds the forefoot. In this design, the fit is accomplished internally and a closure is provided at the rear of the boot. Such boots are commonly referred to as rear-entry boots.
Overlapping-flap boots are the most common type of ski boot. Such boots are often constructed in two pieces with the upper pivotally connected to the lower at about the ankle region. There are, however, so-called three-piece ski boots, which have, in addition to the upper and lower, a front tongue exterior to the shell covering an opening in the top of the boot from the toe area to the area of the shin. In a rear-entry boot, the rear portion of the shaft surrounding the lower leg can be considered to be a combination of overlapping flaps in the manner of a three-piece boot's lower. The principle of closure is the same.
Early boots were closed with laces which applied a rather uniform pressure on the foot, but were time consuming to close, difficult to tighten and difficult to adjust while skiing.
Later, buckles such as are disclosed in my U.S. Pat. No. 4,051,611, were applied to the overlapping flaps providing a faster and more adjustable closure system. These devices can apply higher forces to more easily close modern, relatively stiff, plastic ski boots. Buckles are also the most common means of closing rear-entry type boots about the lower leg, differing only from the front-entry design in position of the catches and latches on the shell.
In conventional overlapping front-entry boots, at least one buckle is provided for closing the upper portion about the shin area. Best adjustment of the lower over the fore-foot is provided by two buckles, one near the front end of the metatarsals and one in the region of the instep. Two buckles accommodate the great differences in slope and size of the insteps of individual feet and allow for different degrees of tightness at these areas. While a single buckle closure lever would be more desirable, it is difficult to design one mechanism in the limited space presented on the side of the boot shell which still keeps the adjustment and independent action desired. Thus, one drawback to existing closure systems employing two or more buckles is that each latch must be individually connected to and disconnected from a catch every time the boot is put on and taken off.
The known ski boot buckle systems are also disadvantageous in that they prevent a sleek appearance to the boot. Buckles also tend to catch on other objects while walking or skiing, for example door frames, ski-racing poles, etc, and they cause added wind resistance, a disadvantage in downhill ski-racing or speed trials.
In addition, the major disadvantage of the known buckle systems is that they apply forces to the ski boot shell mainly in the localized area of their attachment. The buckles must be attached to the shell in relatively specific locations. If they are too far around the inside half, they interfere with the other boot and ski edges. If too far down on the outside, they hit the snow during skiing or the floor or other objects when walking. As a result, when closed, the catch component and latch component each create, at the points of respective attachment to the shell, radial and tangential components of force and moments. All of the closing forces and moments are concentrated in localized regions of the shell resulting in localized downward pressure on the foot and a tendency to distort the shell into the foot.
The elastic nature of materials used in, e.g. ski boot shell construction, distributes the forces acting on the shell through the lining of the boot to the wearer's foot. Although a tongue is normally positioned over the top of the foot it does not dissipate the highest forces because it must itself be relatively flexible to accommodate the large varieties of foot shapes and amounts of closure of the boot that occur depending on foot shape. Unfortunately, the highest forces are applied to the foot in or near two of the most sensitive areas of the foot, the top of the instep and the side of the foot forward of the outside ankle, causing pain and numbness. The pressures also restrict blood flow causing cold feet in skiing and a tendency to cramp.
Another disadvantage to the known buckle systems is that the forces are applied to the shell at only two points, that is, the position of the catch and the position of the latch. Internal stress in the shell increases from zero at the point of load application to its highest where the sidewall attaches to the sole section of the boot. Therefore, it has been necessary to construct the boot shells with thicker wall sections at the areas of high stress and fatigue. Construction of plastic boot shells in such manner, however, requires molds which are difficult to make and are, thus, costly. It would be much easier and less costly to make a shell with uniform wall thickness. Shells with heavy wall thickness also increases the amount of expensive plastic shell material and increases the weight of the boot, both of which are undesirable. It also requires that the shell be made by the relatively costly method of injection molding rather than a less expensive way, for example, by blow molding which is better suited to articles of relatively uniform wall thickness.
Thus, it is desirable to eliminate conventional buckles from the sides of athletic boots and particularly ski boots. To some extent the aforementioned disadvantages have been eliminated by the so-called rear-entry boots where the closure mechanism is situated at the rear of the boot. In these designs, the foot is held inside a rigid outer shell of fixed shape by an internal fitting system or mechanism such as is disclosed in U.S. Pat. No. 4,160,332. Although such designs provide greater convenience, styling opportunities and comfort, they do not hold the foot and lower leg as well as overlapping flap boots and consequently do not ski as well. Furthermore, the internal fitting mechanisms of present rear-entry boots are unable to provide optimum close fit, usually because they act on a relatively small area of the foot and cannot encase the entire foot.
In another approach to eliminate the pressure concentration of buckle systems, a ski boot is known which has buckles attached to stainless steel straps surrounding the forefoot in the traditional buckle locations. These straps still do not eliminate the radial components of force and the moments about the connections that cause comfort problems. Rather the extra width of the strap where the latch and catch are attached only serves to spread the load from the buckle over a slightly wider area.
Accordingly, it is an object of the present invention to provide a closure system for athletic boots and particularly ski boots which allows greater comfort and convenience, streamlining, reduced weight and cost, and improved styling possibilities, while retaining the fit and performance inherent in the design of front-entry boots.
It is another object to provide a closure system for ski boots and other footwear which applies closing forces perpendicularly to the boot shell at any point around the foot rather than tangentially whereby a more uniform pressure distribution is applied to the wearer's foot.